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Palythoa grandis: cautions required!

Palytoxins are back under the spotlight! Coral Biome breeds in its facility some potentially toxic zoanthids. To get the bottom of it, we carried out a study based upon the same protocol described by Jonathan Deeds and his colleagues in the “Plos One” journal in 2011, a publication previously discussed on our blog.First, we investigated the phylogenetic relationships of some species including the famous Palythoa grandis, a rare endemic species living in deep waters of the Gulf of Mexico. The determination of the phylogenetic relationships of this species is important because, according to Deeds and coll., it exists a close link between the membership of a species to a given clade and its potential toxicity. Therefore we analyzed the DNA sequence coding for the large subunit mitochondrial ribosomal RNA (rRNA16S) of P. grandis. Our phylogenetic reconstruction suggested the potential toxicity of this species. Indeed, P. grandis grouped with P. heliodiscus, a species known for its high concentration of palytoxin and listed among the most toxic zoanthids in the Deeds study.To confirm the toxicity of P. grandis, we performed a liquid chromatography analysis of a mixture from a polyp from P. grandis in ethanol. One other unknown species of Palythoa sp. have also been analyzed as well as one specimen of Zoanthus sp. from the Vice Zoa complex.Chromatography principle is to separate different molecules from a mixture. In our study, the detection of molecules was achieved by UV at a wavelength of maximum absorption for palytoxin (263 nm). The material and method used were similar to the Deeds and coll. protocol. These authors observed a retention time for palytoxin about 13 min, a duration we also observed in our analysis for P. grandis (A). A result consistent with its phylogenetic position and its close relationships with the known toxic species P. heliodiscus. The second specimen belonging to an indeterminate species of Palythoa sp. also showed a peak of palytoxin (B) while the Zoanthus Vice Zoa (C) did not. The absence of peak for Zoanthus considered here as a negative control confirms the higher toxicity of Palythoa versus Zoanthus as previously shown in the Deeds and coll. study.Therefore, P. grandis likely contains a concentration of palytoxin potentially dangerous for Human. Some cultured species in our tanks exhibit high rates of palytoxin, important enough to justify elementary precautions when handling them: use of gloves and protective goggles.
Special thanks to Robert at the University of Aix-Marseille for his help in chromatographic analysis. This work was directed by Pierre Maziani, undergraduate student of Biology. A big thank to its availability, its rigor … and good humor!